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Walk-in freeer Compressor blowing start caps

walk in freezer having issues
Some other company converted the old system from a water cooled condenser to a air cooled condenser which is still located inside the restaurant. approx 4 yrs old
My buddy from work gets called in saying their freezer down, he found a bad start cap, so he replaced it and it worked fine. A few days later i get called back to this site and same thing. Top of the compressor is extremely hot and it wont start. Investiated and discovered start capibilties gone again. start cap is blown. I replaced the start cap run cap and the potential relay (took down the compressor info and got the correct parts for that compressor) Also cleaned the condenser for good measures. incase its getting too high head.
Replaced the parts checked pressures and amps everthing is fine. I got advised by my boss that the compressor is on its way out and to let the manegers know about issue. Now today i get called from my boss that the system is down again. Same issue, but this time he went there to talk to maneger. we are looking to replace the compressor in a few days or even installing a condenser for the roof due to the temperature inside the restaurant.

Just curious is this common thing to happen that this compressor is having a hard time starting and blowing the starting components. is this a good sign of the compressor being bad? Thinking that the people that put in this system didnt do their job of doing a proper vacuum or dirty refrigerant. Is there any other issues that may cause this to fail?

Just wanting some input much appreciated

Last edited by akelesis; 10-27-2012 at 03:45 PM.

Get er Done!

Do what has to be done
when it has to be done
as well as it has to be done
And doing it all the time.

Personally, I would say this isn't necessarily a 'common' problem as oftentimes mechanical wear will completely lock the pump up or burn out the start winding - and prolonged low voltage/short cycling will usually cause a catastrophic electrical failure in the motor (start) winding long before taking out several start capacitors in succession.

Just shooting from the hip, if your voltage is ok, I'd tend to be of the same opinion as your boss at this point.

"The problem is the average person isn’t tuned in to lifelong learning, or going to seminars and so forth. If the information is not on television, and it’s not in the movies they watch, and it’s not in the few books that they buy, they don’t get it" - Jack Canfield

Does it have a CPR valve? An incorrectly adjusted or faulty/nonexistent crankcase pressure regulator valve can cause the same symptom. Excessive crankcase pressure can cause a hard start condition and subsequently kill your start capacitor.

That CPR is a big issue if it occurs after defrost. You can actually observe this after defrost it will literally bring start circuit in and out many times. K body (small air cooled) Copelands are especially prone to this.

Failure of the defrost termination circuit will aggravate the problem as the evap will overheat during defrost

Check all switches in the control circuit to the contactor coil. Usually when we run into this it is either short cycling as already stated, or a problem with a pressure switch where the switch instead of snapping positively open and remaining open, will open/close/open/close/open/ close repeatedly until something blows....start capacitor.

Check all switches in the control circuit to the contactor coil. Usually when we run into this it is either short cycling as already stated, or a problem with a pressure switch where the switch instead of snapping positively open and remaining open, will open/close/open/close/open/ close repeatedly until something blows....start capacitor.

Not just pressure switches, either. Recently, I had an ice machine condenser that locked out on shutdown. I replaced the low pressure switch because of the heavy use, but it was poor continuity of the contactor that was the power source for the pressure switches in the condensing unit, and when the contactor chattered it pulled down the voltage in the 208 volt safety circuit, which in turn, meant a loss of coil voltage in the contactor. New switch, new contactor, done deal.